Method of sharpening punches or the like



June 1930- s. N. TEVANDER 1,766,964

IETHOD 0F SHARPENING PUNGHBS OR THE LIKE rma Sept. 1929 gzwembr ,5?! 430 c: fillies: a: 3.

Patented June 24, 1930 UNITED STATES SWAN N. TEVANDER, F MAYWOOD, ILLINOIS METHOD OF SHARPENING- IETUNCHES OR THE LIKE Application filed September a, 1929. Serial No. 390,788.

The purpose of this invention is to provide an improved method of sharpening or dressing tools such as punches, dies, etc.,iwhe reby the sharpening may be performed accurately and expeditiously without removing the punch from the machine in which it is employed, thus efiecting a substantial saving in time and cost. It consists in certain novel sequence of steps as herein shown and described and as set forth in the claims.

In the drawings:

Figure 1 is fragmentary View of a punch and die shown partly in section with the sharpening element in operative relation for carrying out the method embodying the present invention.

Figure 2 is a bottom plan view showing the sharpening element in operative relation to the punch; other positions of the tool being indicated in dotted lines.

Figure 3 is a fragmentary View showing the punch passing through its co-operating die for trimming olf the excess material around its cutting edge.

It is well known to those who are familiar with the art of sheet metal punching that after a punch has been in use for a period of time its cutting edges wear dull and usually become reduced in size. There are various methods of replacing the cutting edges of a punch and the most common practice heretofore employed is effected by hand and consists in upsetting the cutting edge by swedging or peening with a special hammer to increase the size of the cutting edge of the punch beyond normal and then passing the punch through the die to trim 05 the wire edge which will represent the excess enlargement produced at the cutting edge by the O peening operation. Special skill is required to put a good uniform edge on a punch in this manner and the method is both tedious and inaccurate. Furthermore, this hand method frequently necessitated removing the punch from its machine because of the limited space otherwise available for the hammer strokes.

Another method frequently employed consists in removing the punch and placing it in a chuck by means of which it is rotated against a series of tapered rollers which cause upsetembodying the present invention is similar to that disclosed in my PatentNo. 1,751,113, issued March 18, 1930. For the purpose of making my improved method more clearly understood, a brief description of the apparatus illustrated will be given. in Figure 1 a fragmentary portion of a machine is shown and consists of a punch indicated at 11, and a co-operating die, 12, mounted on the base plate, 13. It is to be understood that the sharpeningtool is of a portable nature so as to permit operation on the cutting edge of the punch (indicated at 14) while the latter remains in its normal position in the machine. The tool consists of a rapidly rotatable element, 15, of polygonal cross-section having aplurality of flat faces, 16. The corners of the contiguous faces are preferably rounded or chamfered as indicated at l'ito obviate possible denting or nicking of the cutting edge of the punch during the sharpening operation which would be likely to re- ,sult if these corners were sharp. The rotary element is mounted on a rigid shaft, 19, the

latter-in turn being connected to a flexible shaft, 20, which may be driven from any suitablesource of power such as a portable electric motor (not shown) the rotary element being secured on the shaft against the shoulder, 19 by means of lock nuts, 21. A

stationary handle, 23, is secured to the tubular casing, 24, of the flexible shaftand provides a convenient hand grip for the operator for directing the rotary elementagainst the cut tingedge of the punch.

The rotary element may be made of considerably harder material than the punch and due to its rapid rotation when directed against the cutting edge of the punch the impacts of itsblunted or rounded edges, 17, act as hammer blows thereagainst and serve to upset or swage the cutting edgevery quickly forcing the material to flow outwardly as indicated at 14* in the drawing. It is to be understood that the rotary element is applied to successive portions of the cutting edge of the punch while the punch remains in its machine and as indicated in Figure 2 the tool has been moved from the dotted position indicated at A to the position shown in full through which range of movement the cutting edge of the punch has been swedged or upset. The other dotted positions of the tool indicated at B and C respectively represent positions that the tool will'assume as it progresses over successive portions of the cutting edge of the punch. It is to be understood that the swedging or upsetting of the cutting edge of the punch increases the diameter of the cutting edge beyond normal and after the cutting edge of the punch has been completely upset it is then passed through its co-operating die as shown in Figure 3 to trim off this excess or wire edge, thus reducing the cuttin edge of the punch to the proper size.

My improved method of upsetting the cutting edge of a punch or the like can be effected uniformly and accurately even by an unskilled operator and manifestly more expeditiously than by the method employing the hani hammer. By this improved method the operator manually controls the shifting of the rotary element which is also of advantage in that it permits regulating the amount of application of the rotary element to cause swedging; this feature is especially important where the cutting edge of the punch has a nick or a hard spot. Furthermore, the fact that the upsetting of the cutting'c-dge of the punch may be accomplished while the punch remains in the machine in which it is employed effects a substantial saving in time and cost by eliminating the resetting and locating the punch in the machine, which frequently consumes a considerable amount of time where the set up is difficult or intricate. Since the manipulation of the rotary element is under full control of the operator at all times the cutting edges of punches of relatively complicated design may be easily worked upon.

I claim:

1. The method of sharpening the cutting edge of a punch or the like consisting in applying a rapidly rotating element of noncircular cross-section to successive portions of the cutting edge of the punch while the punch remains in normal position in its machine for causing uniform swedging or upsetting of the cutting edge to a size in excess of normal, then passing the punch through its cooperating die to trim off the excess material, thereby restoring the cutting edge of the punch to proper size.

. 2.. The method of sharpening the cutting edge of a punch or the like consisting in directing against the cutting edge a substantially polyhedral rotary element so that the surfaces thereof impinge against said cutting edge in rapid succession as hammer blows for upsetting the cutting edge to a size in excess of normal, then trimming off this excess to restore the cutting edge to proper size.

3. The method of sharpening the cutting edge of a punch or the like consisting in directing against the cutting edge of the punch, while the same remains in a normal non-rotative position in its machine, a polyhedral rotary element so that the surfaces thereof impinge against said cutting edge in rapid succession as hammer blows for upsetting the cutting edge to a size in excess of normal, shifting said rotary element to permit it to operate successively upon different portions of said cutting edge, and then trimming ofi the excess to restore the cutting edge to proper size.

4;. The method of sharpening the cutting edge of a punch or the like consisting in manually directing against the cutting edge a polyhedral rotary element so that the surfaces thereof impinge against said cutting edge in rapid succession as hammer blows for upsetting the cutting edge to a size in excess of normal, then passing the punch through its co-operating die to trim off the excess material, thereby restoring the cutting edge of the punch to proper size.

In testimony whereof, I have hereunto set my hand at Chicago, Illinois, this 3rd day of September, A. vD. 1929.

' SNAN N. TEVANDER. 

